TechThrive is an interactive artwork that blossoms like a living flower—its petals unfurl with every passerby’s movement, while its radiant androecium blooms are shaped by soaring flight paths overhead.

At the heart of the piece lies Atlanta’s airport (ATL), from which graceful arcs radiate outward like filaments of an androecium—representing flights, far-reaching connections, and the mixing of ideas—forces we cannot fully control. Encircling this core is a vibrant, pulsing field of color, brought to life by your own movements here and now. When you move, it glows. When you pause, it softens and fades. Go ahead, try it for yourself!

This artwork is co-created by two forces: the actions we choose and the ones that unfold on their own. It reminds us that beauty emerges not only from our purposeful steps, but also from the unseen, unbidden patterns around us.

Much like this artwork, isn’t life too a blend of what we can shape and what lies beyond our control? It’s beautiful to recognize how much color we bring to the spaces around us. And yet, there is peace and joy in watching the world move on its own.

TechThrive is a reflection on both agency and entrustment; on doing and being, on purposeful action and letting go. May it remind us of the joy we create by moving through the world with intention, and the calm that comes from letting the rest unfold.

Wireless signals emitted by a wireless device, such as a Wi-Fi access-point, spread in all directions. Some of those signals are reflected by the things in the environment and reach back to the access-point. Things made of metal are good reflectors of wireless signals, and so is water. Incidentally, our bodies are made of about 70% water, making our bodies good reflectors of wireless signals.

In this work, we use a special type of wireless signals called ultra-wideband (UWB) signals. These wireless signals use a lot of wireless frequencies to make a short pulse that can be easily recognized even when it has reflected from many objects. In fact, we are able to separate out reflections coming from objects or people just a few feet from each other. We analyze each of the reflections carefully and represent the time delays of the reflections and the intensity of these reflections are colored bubbles.

The closer the reflection comes from, the closer its corresponding bubble from the art's central core. The further the reflection, the further is its bubble. The more prominent the reflection, the larger is its corresponding bubble. The system continuously learns about static reflections and then slowly removes their influence. That is how we avoid the reflections from the ceiling and the floor and other static objects around this display from overwhelming the art. When you move in the vicinity, it largely influences direct reflections which you see as large bubbles, probably yellow or green or bluish in color. But your presence also changes second and third order reflections which appear further away from the center, and might be dark blue or purple.

What about the flight paths?
We have collected the historical flight data from opensky-network.org about flights to and from Atlanta Airport (ATL). We have put ATL at the center and then have divided the screen to map the earth's latitude and longitude across its height and width. We take a little bit of artistic liberty; the coordinates are a little skewed to make it look good and really far away places go out of the screen. The little dots traveling along the flight trajectory represent movement of people.

Yes, a lot of it!

We mentioned that the wireless signals used are called UWB signals. These are made of short pulses generated from a combination of millions of sine-waves with slightly different frequencies. A lot of frequencies means a large bandwidth and hence the name: ultra-wideband (UWB). When these pulses arrive back at the UWB wireless receiver, we get a mix of the echoes coming from the transmitted signal delayed several times due to reflections. Each of these reflections has a different amplitude, and a different phase than the transmitted signal.

Mathematically, $$y(t) = \sum_i a_i x(t-\tau_i)e^{j(2\pi f_c(t-\tau_i))+\Delta T}$$ where, y(t) represents the received signal. The original transmitted signal $x(t)$ is delayed by a different time delay (usually in nanoseconds), denoted by $\tau_i$ each reflection is represented by $i$, its amplitude is represented by $a_i$. The phase of the carrier frequency (also called the central frequency) $f_c$ is also changed due to the delay. The transmitter adds an arbitrary phase offset $\Delta T$, which does not depend on the signal delays.
This received signal would remain constant if nothing changed in the environment (except for the $\Delta T$ which changes every time the transmitter sends a signal). But if the environment changes, say, due to the movement of people around this display, some of the signal's paths are altered. We accumulate several received signals over time (forming an idea of how the reflections look like on an average) and then continuously compare the current signal with the accumulated average. Large changes from the average are represented as large bubbles, and small deviations result in small bubbles.
Since we use a UWB transmitter and another receiver, the first signal we receive is the direct signal between the transmitter and the receiver. This forms a reference point and all comparisons are done from the time at which the transmitted signal first appears at the receiver. Incidentally, treating the unchanging direct signal between the transmitter and the receiver as the reference point, also allows us to remove the effect of the arbitrary transmitter phase $\Delta T$. This time is denoted as the center in the artwork. Changes that are closer appear as larger bubbles near the center, and changes that are further away appear as bubbles further from the center. The colors follow the standard hue patterns in a color wheel starting from red used for the closest reflectors to violet for the furthest.
Each received signal and its reflections are plotted radially to depict passage of time. To do so, we plot on a horizontal line from the center and then rotate the line according to standard 2D rotation matrix given by: $$ \begin{bmatrix} x' \\ y' \end{bmatrix} = \begin{bmatrix} \cos\theta & -\sin\theta \\ \sin\theta & \cos\theta \end{bmatrix} \begin{bmatrix} x \\ y \end{bmatrix} $$ where $\theta$ denotes the angle by which we must rotate the current signal's deviations from the average.

What about the flight paths?
The GPS coordinates of the destination airport (latitude and longitude) are used to determine the endpoint of the curve. The flight paths are drawn using Bezier curves. The lift (or curvature) given to each Bezier curve depends on the distance traveled. The little specks of dots along the flight path are generated using Gaussian noise around the Bezier curve.

Yes, a lot of it!

Wireless signals are electromagnetic waves. They travel at the speed of light which is $299{,}792{,}458\,m/s$ or approximately $186{,}000$ miles per second. This means two reflections separated by about 1 foot will appear about one nanosecond apart (that is one billionth of a second!) in time.
We use wireless signals at the central frequency of $4\,GHz$. Many common materials such as wood, plastic, glass are all transparent to this electromagnetic frequency. But water is not transparent at this frequency. Yes, whether an object is transparent or opaque depends on the incident signal's frequency. In the same vein, refractive index of a substance is also frequency dependent... but I digress. In fact, water reflects almost 86% of the signal's energy at these frequencies. Since the human body is made of mostly water, our bodies act like mirrors for wireless signals. That is why we are able to capture reflections and compare their relative strengths.

What about the flight paths?
While there is a lot of physics involved in flying an airplane, we are just drawing their approximate paths as Bezier curves.

Yes, a lot of it!

We use Processing.org to generate the graphics. Processing is an open project initiated by Ben Fry and Casey Reas. It is developed by a team of contributors around the world.

The graphics are layered with the UWB signal reflections shown on the bottom-most layer. One line of circles derived from the wireless signal disturbances is added to this layer at every time step and the layer is rotated to create the clock-like effect. Above this layer are the flight paths generated by mapping the latitude-longitude of the destination airports to x-y coordinates on the screen. The flight data comes from opensky-network.org. Finally the little specks of dots are a third layer. The dots follow the Bezier curve.

Live data from the UWB device is loaded to the computer using Serial over USB. The data arrives as ASCII text and is parsed and interpreted by the graphics program.

Finally, a frame-fader routine fades out older screen contents to make space for newer live data.

TechThrive uses two UWB devices, one acts as a transmitter and another as a receiver to capture reflections. You would need two UWB devices to observe the reflections. Even then, today's smartphones with UWB are not designed to capture and expose the detailed reflection patterns obtained through the UWB channel impulse response. So, while your UWB-enabled phone might have the same underlying hardware, it cannot support TechThrive because of software limitations.
UWB is a versatile sensor. As more use-cases become enabled, perhaps even through research projects like this one, phone manufacturers might open up additional capabilities.

TechThrive is a one-of-its-kind research prototype developed specifically for the Atlanta Airport. Currently, there are no other TechThrive installations. It is derived from the TechMyMoves exhibit at Georgia Tech library (Aug-Oct 2022).

However, this technology could be used to develop new exhibits for museums, artist backdrops, sporting events, music festivals, etc. If you would like to see this technology in your space, read the following section on "Sponsoring a UWB project".

If you would like to sponsor a UWB research project or a new custom art installation, please contact me over email: dhekne [at] gatech [dot] edu. I will route your sponsorship request through the Office of Sponsored Research at Georgia Tech.

A list of research projects developed by my group at Georgia Tech is here.